This invention pertains to a new method for treating pain, inflammation, trauma, allergy, and disease by the topical application of a therapeutic agent having previously unrecognized analgesic, anti-allergenic, and anti-inflammatory properties, or by the topical application of the same agent in combination with a second therapeutic agent, the effectiveness of which is enhanced by the first agent.
As stated in the publication of Texaco Chemical Company entitled "Ethylene Carbonate-Propylene Carbonate," "Propylene Carbonate is a clear, mobile, practically odorless liquid." It is 4-methyl 2-dioxolone, a cyclic organic ester which is a known solvent for a variety of polar and non-polar organic compounds and for many inorganic chemical and biological materials. Its chemical properties include low toxicity. The same publication further indicates that propylene carbonate is an excellent additive for certain clays and gel bases useful in cosmetic and personal care products. Still further, the publication refers to acute toxicity tests which indicate that propylene carbonate is practically non-toxic and is otherwise indicated to be non-offensive in subchronic dermal applications, skin sensitization tests and inhalation tests, though temporarily offensive to a minor degree to the eyes.
The Texaco publication also includes a extensive bibliography, including an applications section entitled "Cosmetics and Personal Care," in which four patent references and three literature references are noted.
No indication whatsoever is found in the above-referenced Texaco publication to suggest, in any way, the possible utility of propylene carbonate as a therapeutic agent for treating pain, inflammation, trauma, allergy, or disease.
A search has been conducted in the U.S. Patent and Trademark Office to identify references relating to or disclosing the use of propylene carbonate for essentially any pharmaceutical purpose. Patents identified in this search were:
______________________________________ U.S. PAT. NO. INVENTOR ______________________________________ 4,017,615 Shastri, et al. 4,279,901 Ronald M. Kudla 3,924,004 Chang et al. 4,273,770 Francisco Alvarez 4,242,334 Stache et al. 3,829,826 Gaetano D'Alelio 3,574,118 Wayne Otto Baker 3,362,927 Edwin H. Lochridge 3,185,627 Gus S. Kass 3,178,352 Roy Erickson 3,136,696 Benjamin Harrison 3,472,931 R. B. Stoughton 4,244,942 Kamishita et al. 3,298,919 Jack L. Bishop, Jr. 3,352,753 Leonard J. Lerner ______________________________________
The first three of the above-listed patents are listed in the Application-Cosmetics and Personal Care subsection of the bibliography in the above-referenced Texaco Chemical Company publication (page 24). The primary focus of Kudla is on ethylene carbonate rather than propylene carbonate. It will also be noted that the remaining references in that bibliography subsection all deal only with hair-treatment preparations. The patents on Chang, Shastri et al., and Kudla all relate to topical ointment compositions in which, generally, propylene carbonate or ethylene carbonate is combined with co-solvents or with other constituents, such that only a minor proportion of propylene carbonate is included in each composition, generally less than 40% in Chang and 30% in Shastri, for example. The compositions, in which propylene carbonate is incorporated in accordance with the teachings of these patents, each include specific therapeutic agents, such as anti-biotics, steroids, antihistamines, antiseptics, anesthetics, and corticosteroids.
The D'Alelio patent relates to the use of propylene carbonate in removing dental calculus, relying on its non-toxic solvent function for swelling the organic binder phase of the calculus.
Alvarez is directed to novel anti-inflammatory agents. It indicates, however, that such agents may be combined with a "pharmaceutically acceptable solvent," among particularly suitable examples of which is listed propylene carbonate. As in other applications of this type, the carbonate is generally carried in a semi-solid emulsion of oil and water, or water in oil including, for example, white petrolatum.
The Stache patent was cited apparently for its teaching of various carbonate-containing steroids useful in veterinary and human therapy. Notably absent, according to Applicants' reading of this patent, is any suggestion of the use of propylene carbonate in any manner different than that suggested in the other prior art references, cited above.
In addition to the foregoing, Applicants are aware of certain unpublished non-clinical work of others. Applicants' limited knowledge of this work prior to the present invention, indicated that propylene carbonate had been considered only for possible use as a rapid surface skin-penetrating carrier for a topically applied composition, namely suntan lotion, the objective of which was to eliminate the greasy surface feel commonly associated with existing suntan lotion. It is not known whether any such suntan lotion was ever prepared.
Notwithstanding prior knowledge of propylene carbonate and its limited use as a vehicle in topical medicaments, and notwithstanding the unpublished work of others suggesting propylene carbonate as a vehicle for suntan lotion, there remains a continuing need for more effective methods of therapy to relieve pain and inflammation and to treat trauma, allergy, and disease. This need has not been addressed in the art pertaining to propylene carbonate.
It is, therefore, the general object of the present invention to provide such a method by the topical application of a hitherto unrecognized therapeutic agent, either alone or in combination with a second agent, the therapeutic effectiveness of which is enhanced by the first agent.